MRAM is rapidly replacing conventional memory. One critical aspect of the MRAM technology development is forming a magnetic tunnel junction (MTJ) structure for MTJ memory devices. However, conventional integration schemes requires chemical mechanical planarization (CMP) for planarization before forming a top electrode, e.g., a via or trench filled with conducting material over the MTJ structure. The top electrode is much dependent on the planarization step and it may damage the MTJ structure without proper planarization. To achieve a flat surface, a closer MTJ density to memory array is required across the chip to have a good CMP uniformity. On the other hand, end point detection is usually used in the top electrode opening step to avoid excessive etch which damages MTJ. A higher MTJ density is required to achieve a stronger end point detection signal. The conventional MTJ dummy placement depends much on the upper and lower interconnects. The intrinsic density is hence constrained by the upper and lower interconnects and it is not easy to achieve uniformity in dummy fill with density close to memory array.
A need therefore exists for methodology enabling a flexible dummy fill to increase MTJ density and the related device.